RESONANT CONVERTING APPARATUS AND CONTROL METHOD THEREOF
A resonant converting apparatus and a control method thereof are provided. The resonant converting apparatus includes a resonant converting circuit, a load detector, a control signal generator and a pulse frequency modulation (PFM) signal generator. The resonant converting circuit converts an input voltage into an output voltage to drive a load according to a PFM signal. The load detector detects a load status of the load. The control signal generator generates the control signal according to the load status and a PFM range. When the load status is a light load status, the control signal is divided into a plurality of first time periods and second time periods which are respectively arranged alternatively. The PFM signal is maintained to a reference voltage during the second time periods, and is a periodical signal having frequency substantially equal to a resonant frequency during the first time periods.
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This application claims the priority benefit of China application serial no. 201610555594.1, filed on Jul. 13, 2016. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION Field of the InventionThe invention relates to a resonant converting apparatus and a control method thereof, and particularly relates to a resonant converting apparatus and a control method thereof capable of improving power conversion efficiency under a light load status.
Description of Related ArtAlong with development of electronic science and technology, electronic apparatuses have become important tools in people's daily life. In order to make the electronic apparatus to satisfy the need of multi-function, the electronic apparatus generally requires a plurality of different power supplies, so that a power converter becomes an important device in the electronic apparatus.
Regarding a conventional series resonant converter, a working state thereof has optimal efficiency when a switching frequency of a switch thereof is close to a resonant frequency provided by a resonant trough in the series resonant converter. However, in an actual practise, when a load of the series resonant converter is decreased, a required output current is decreased. Therefore, in order to produce a stable output voltage, the switching frequency of the switch of the series resonant converter is raised, and the switching frequency of the switch is away from the resonant frequency provided by the resonant trough, which decreases of the power conversion efficiency.
SUMMARY OF THE INVENTIONThe invention is directed to a resonant converting apparatus and a control method thereof, which effectively improve power conversion efficiency under a light load status.
The invention provides a resonant converting apparatus including a resonant converting circuit, a load detector, a control signal generator and a pulse frequency modulation (PFM) signal generator. The resonant converting circuit receives an input voltage, and converts the input voltage to produce an output voltage according to a PFM signal, and the resonant converting circuit provides the output voltage to drive a load. The load detector is coupled to the resonant converting circuit, and detects a load status of the load. The control signal generator is coupled to the load detector and the resonant converting circuit, and generates a control signal according to the load status and a PFM range. The PFM signal generator is coupled between the control signal generator and the resonant converting circuit, and generates the PFM signal according to the control signal. When the load status is a light load status, the control signal generator divides the control signal into a plurality of first time periods and a plurality of second time periods according to the PFM range, where the first time periods and the second time periods are arranged alternatively, and the PFM signal generator keeps the PFM signal at a reference voltage during the second time periods, and sets the PFM signal to a periodical signal having frequency substantially equal to a resonant frequency during the first time periods.
In an embodiment of the invention, the control signal generator detects a current demand of the load to obtain the load status.
In an embodiment of the invention, the control signal generator determines the load status to be the light load status when the current demand is smaller than a predetermined threshold.
In an embodiment of the invention, the control signal generator adjusts time lengths of the first time periods and the second time periods according to a variation of the current demand when the load status is the light load status.
In an embodiment of the invention, the current demand is positively correlated to the time length of each of the first time periods.
The invention provides a control method of a resonant voltage converter, which includes following steps: detecting a load status of a load driven by the resonant voltage converter; generating a control signal according to the load status and a PFM range; generating a PFM signal according to the control signal, where when the load status is a light load status, the control signal is divided into a plurality of first time periods and a plurality of second time periods according to the PFM range, and the first time periods and the second time periods are arranged in alternation, and the PFM signal is maintained to a reference voltage during the second time periods, and is a periodical signal having frequency substantially equal to a resonant frequency during the first time periods; and converting an input voltage to generate an output voltage according to the PFM signal.
According to the above descriptions, under the light load status, the control signal is divided into a plurality of first time periods and a plurality of second time periods, and the resonant conversion circuit does not perform the switching operation during the second time periods under control of the PFM signal, and the PFM signal makes the switch of the resonant converting circuit to substantially perform periodic switching operation during the first time periods according to a corrected resonant frequency. In this way, the frequency of the PFM signal is not away from the resonant frequency, by which the power conversion efficiency of the resonant converting apparatus under the light load status is improved.
In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The control signal generator 120 is coupled to the load detector 130 and PFM signal generator 150. The control signal generator 120 provides the control signal CTR to the PFM signal generator 150 to control generation of a PFM signal PFM of the PFM signal generator 150. The PFM signal generator 150 is coupled to the resonant converting circuit 110, and provides the PFM signal PFM to the resonant converting circuit 110. The resonant converting circuit 110 performs a switching operation of a switch according to the PFM signal PFM, and performs a power conversion operation to convert the input voltage VIN into the output voltage VOUT through the switching operation of the switch.
In view of an operation detail, the control signal generator 120 receives the load status provided by the load detector 130, and the control signal generator 120 adjusts the control signal CTR according to the load status and a PFM range, where the PFM range is determined according to an output voltage feedback signal of the load 140. In the present embodiment, a pulse frequency is a periodical signal having frequency substantially equal to a resonant frequency. It should be noted that when the load status indicates that the current demand of the load 140 is the light load status, in the present embodiment, the control signal generator 120 divides the control signal CTR into a plurality of first time periods and a plurality of second time periods according to the PFM range, where the first time periods and the second time periods are arranged in alternation. The control signal CTR can be held on a first reference voltage during the first time periods, and be held on a second reference voltage during the second time periods, the first reference voltage can be higher than or lower than the second reference voltage.
Moreover, the PFM signal generator 150 receives the control signal CTR, and generates the PFM signal PFM corresponding to the first and second time periods according to the control signal CTR. The PFM signal is a periodical signal during the first time periods, where a frequency of the periodical signal is substantially equal to the resonant frequency of the resonant converting circuit 110, and the PFM signal is held on a reference voltage during the second time periods.
Referring to
It should be noted that time lengths of the first time periods T1 and the second time periods T2 are not limited. When the load detector 130 determines that the resonant converting apparatus 100 is in the light load status, the control signal generator 120 may further adjust the time lengths of the first time periods T1 and the second time periods T2 according to a variation of the current demand of the load 140. When the current demand of the load 140 is decreased, the time length of the first time period T1 can be reduced, and the time length of the second tune period T2 can be corresponding increased. Conversely, when the current demand of the load 140 is increased, the time length of the first time period T1 can be increased, and the time length of the second time period T2 can be corresponding reduced. Namely, the time length of the first time period T1 is positively correlated to the current demand of the load 140, and the time length of the second time period T2 is negatively correlated to the current demand of the load 140.
Referring to
Comparatively, in
Referring to
The second side rectifying circuit 420 is coupled to the secondary side W2 of the transformer 440 to receive the third voltage V3. The second side rectifying circuit 420 rectifies the third voltage V3 to generate the output voltage VOUT.
In the present embodiment, the resonant converting circuit 400 can be a series resonant converting circuit or a series parallel resonant converting circuit, a parallel resonant converting circuit. A resonant trough formed by the inductor Lr and the capacitor Cr in the inductance capacitance resonant circuit 430 provides a resonant frequency. Moreover, the inductor Lr can be coupled to an external inductor LE.
Implementation detail of the first side converting circuit 410 of the present embodiment may refer to
Referring to
The first side converting circuit 440 in
The first side converting circuit 440 in
In the present embodiment, the first side converting circuit 440 further includes capacitors C1 and C2. One terminal of the capacitor C1 receives the input voltage VIN, and another terminal of the capacitor C1 is coupled to the terminal A. The capacitor C2 is connected in series between the terminal A and the reference ground terminal GND.
On the other hand, implementation detail of the second side rectifying circuit 420 of the present embodiment is described below. Referring to
In
On the other hand, in
In
It should be noted that any one of the aforementioned first side converting circuits 410 and any one of the aforementioned second side rectifying circuits 420 can be combined with each other to Rain the resonant converting circuit 400 of the present embodiment. Certainly, the first side converting circuits 410 and the second side rectifying circuits 420 are not limited to the aforementioned descriptions, and any converting circuit and rectifying circuit known by those skilled in the art can be applied to the invention.
Referring to
Implementation details of the aforementioned steps have been described in the aforementioned embodiments, and details thereof are not repeated.
In summary, in the light load status of the resonant converting apparatus of the invention, the control signal used for controlling switching of the switches is divided into a plurality of first time periods and a plurality of second time periods. Moreover, according to the control signal, the PFM signal is the periodical signal having frequency substantially equal to the resonant frequency during the first time periods, and the PFM signal is maintained to the reference voltage during the second time periods. In this way, under the light load status, a switch switching frequency (a frequency of the control signal) of the resonant converting apparatus is not away from the resonant frequency, by which the power conversion efficiency of the resonant converting apparatus under the light load status is effectively maintained.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Claims
1. A resonant converting apparatus, comprising:
- a resonant converting circuit, receiving an input voltage, and converting the input voltage to generate an output voltage according to a pulse frequency modulation signal, and the resonant converting circuit providing the output voltage to drive a load;
- a load detector, coupled to the resonant converting circuit, and detecting a load status of the load; and
- a control signal generator, coupled to the load detector and the resonant converting circuit, and generating a control signal according to the load status and a pulse frequency modulation range; and
- a pulse frequency modulation signal generator, coupled between the control signal generator and the resonant converting circuit, and generating the pulse frequency modulation signal according to the control signal.
2. The resonant converting apparatus as claimed in claim 1, wherein when the load status is a light load status, the control signal generator divides the control signal into a plurality of first time periods and a plurality of second time periods according to the pulse frequency modulation range, the first time periods and the second time periods are arranged alternatively, and the pulse frequency modulation signal generator keeps the pulse frequency modulation signal at a reference voltage during the second time periods, and sets the pulse frequency modulation signal to a periodical signal having frequency substantially equal to a resonant frequency during the first time periods.
3. The resonant converting apparatus as claimed in claim 1, wherein the control signal generator detects a current demand of the load to obtain the load status.
4. The resonant converting apparatus as claimed in claim 1, wherein the control signal generator determines the load status to be the light load status when the current demand is smaller than a predetermined threshold.
5. The resonant converting apparatus as claimed in claim 3, wherein the control signal generator adjusts time lengths of the first time periods and the second time periods according to a variation of the current demand when the load status is the light load status.
6. The resonant converting apparatus as claimed in claim 5, wherein the current demand is positively correlated to the time length of each of the first time periods.
7. The resonant converting apparatus as claimed in claim 1, wherein the resonant converting circuit comprises:
- a first side converting circuit, receiving the input voltage and the pulse frequency modulation signal, and performing a voltage conversion operation to the input voltage based on the pulse frequency modulation signal, and generating a first voltage;
- an inductance capacitance resonant circuit, coupled to the first side converting circuit, providing the resonant frequency, and generating a second voltage according to the first voltage;
- a transformer, coupled to the inductance capacitance resonant circuit, and having a primary side for receiving the first voltage, and having a secondary side coupled to the primary side for generating a third voltage; and
- a second side rectifying circuit, coupled to the secondary side of the transformer, and rectifying the third voltage to generate the output voltage.
8. The resonant converting apparatus as claimed in claim 7, wherein the first side converting circuit comprises:
- a first switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the first switch receives the input voltage, the control terminal of the first switch receives a first pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the first switch is coupled to the inductance capacitance resonant circuit; and
- a second switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the second switch is coupled to the second terminal of the first switch, the control terminal of the second switch receives a second pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the second switch is coupled to a reference ground terminal.
9. The resonant converting apparatus as claimed in claim 8, wherein the first side converting circuit further comprises:
- a first capacitor, having a first terminal receiving the input voltage, and a second terminal coupled to the inductance capacitance resonant circuit; and
- a second capacitor, having a first terminal coupled to the second terminal of the first capacitor, and a second terminal coupled to the reference ground terminal,
- wherein the first voltage is provided between the second terminal of the first capacitor and the second terminal of the first switch.
10. The resonant converting apparatus as claimed in claim 7, wherein the first side converting circuit comprises:
- a first switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the first switch receives the input voltage, the control terminal of the first switch receives a first pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the first switch is coupled to the inductance capacitance resonant circuit;
- a first diode, having a cathode coupled to the first terminal of the first switch;
- a second switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the second switch is coupled to an anode of the first diode and the inductance capacitance resonant circuit, the control terminal of the second switch receives a second pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the second switch is coupled to a reference ground terminal; and
- a second diode, having a cathode coupled to the second terminal of the first switch, and an anode coupled to the reference ground terminal,
- wherein the first voltage is provided between the second terminal of the first switch and the first terminal of the second switch.
11. The resonant converting apparatus as claimed in claim 7, wherein the first side converting circuit comprises:
- a first switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the first switch receives the input voltage, the control terminal of the first switch receives a first pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the first switch is coupled to the inductance capacitance resonant circuit;
- a second switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the second switch is coupled to the second terminal of the first switch, the control terminal of the second switch receives a second pulse frequency modulation signal of the pulse frequency modulation signal, and the second terminal of the second switch is coupled to a reference ground terminal;
- a third switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the third switch receives the input voltage, the second terminal of the third switch is coupled to the inductance capacitance resonant circuit, and the control terminal of the third switch receives the second pulse frequency modulation signal; and
- a fourth switch, having a first terminal, a second terminal and a control terminal, wherein the first terminal of the fourth switch is coupled to the second terminal of the third switch, the control terminal of the fourth switch receives the first pulse frequency modulation signal, and the second terminal of the fourth switch is coupled to the reference ground voltage,
- wherein the first voltage is provided between the second terminal of the first switch and the second terminal of the third switch.
12. The resonant converting apparatus as claimed in claim 7, wherein the second side rectifying circuit comprises:
- a first diode, having an anode coupled to a first terminal of the secondary side;
- a second diode, having an anode coupled to a second terminal of the secondary side, and a cathode coupled to a cathode of the first diode;
- an inductor, having a first terminal coupled to the cathode of the first diode; and
- a capacitor, coupled between a second terminal of the inductor and the second terminal of the secondary side.
13. The resonant converting apparatus as claimed in claim 7, wherein the second side rectifying circuit comprises:
- a first diode, having an anode coupled to a first terminal of the secondary side;
- a second diode, having an anode coupled to a second terminal of the secondary side, and a cathode coupled to a cathode of the first diode;
- an inductor, having a first terminal coupled to the cathode of the first diode; and
- a capacitor, coupled between a second terminal of the inductor and a center-tapped terminal the secondary side.
14. The resonant converting apparatus as claimed in claim 7, wherein the second side rectifying circuit comprises:
- a first diode, having an anode coupled to a first terminal of the secondary side;
- a second diode, having an anode coupled to a second terminal of the secondary side, and a cathode coupled to a cathode of the first diode;
- a third diode, having a cathode coupled to the first terminal of the secondary side, and an anode coupled to a reference ground terminal;
- a fourth diode, having a cathode coupled to the second terminal of the secondary side, and an anode coupled to the reference ground terminal;
- an inductor, having a first terminal coupled to the cathodes of the first diode and the second diode; and
- a capacitor, coupled in series between the second terminal of the inductor and the reference ground terminal.
15. The resonant converting apparatus as claimed in claim 7, wherein the second side rectifying circuit comprises:
- a first inductor, having a first terminal coupled to a first terminal of the secondary side;
- a second inductor, coupled between a second terminal of the first inductor and a second terminal of the secondary side;
- a first diode, having an anode coupled to the first terminal of the first inductor;
- a second diode, having an anode coupled to the second terminal of the secondary side, and a cathode coupled to a cathode of the first diode; and
- a capacitor, coupled in series between the cathode of the first diode and the second terminal of the first inductor.
16. A control method of a resonant voltage converter, comprising:
- detecting a load status of a load driven by the resonant voltage converter;
- generating a control signal according to the load status and a pulse frequency modulation range;
- generating a pulse frequency modulation signal according to the control signal,
- wherein when the load status is a light load status, the control signal is divided into a plurality of first time periods and a plurality of second time periods according to the pulse frequency modulation range, and the first time periods and the second time periods are arranged alternatively, and the pulse frequency modulation signal is held on a reference voltage during the second time periods, and is a periodical signal having frequency substantially equal to a resonant frequency during the first time periods; and
- converting an input voltage to generate an output voltage according to the pulse frequency modulation signal.
17. The control method of the resonant voltage converter as claimed in claim 16, wherein the step of detecting the load status of the load driven by the resonant voltage converter comprises:
- detecting a current demand of the load to obtain the load status.
18. The control method of the resonant voltage converter as claimed in claim 17, wherein the step of detecting the load status of the load driven by the resonant voltage converter further comprises:
- determining the load status to be the light load status when the current demand is smaller than a predetermined threshold.
19. The control method of the resonant voltage converter as claimed in claim 17, further comprising:
- adjusting time lengths of the first time periods and the second time periods according to a variation of the current demand when the load status is the light load status.
20. The control method of the resonant voltage converter as claimed in claim 18, wherein the current demand is positively correlated to a time length of the first time period.
Type: Application
Filed: Aug 25, 2016
Publication Date: Jan 18, 2018
Patent Grant number: 9906142
Applicants: LITE-ON ELECTRONICS (GUANGZHOU) LIMITED (GUANGZHOU), Lite-On Technology Corporation (Taipei)
Inventors: Te-Hong Yang (New Taipei City), Ming-Tsung Hsieh (New Taipei City), Yu-Kang Lo (New Taipei City)
Application Number: 15/246,567